The journal isn't the best at being fast, especially when writing
to disk and not to memory, which can cause integration tests to
grind to a halt on beefy systems due to all the systemd-journal-remote
instances not being able to write journal entries to disk fast enough.
Let's introduce an option to allow writing in progress test journals
to use /tmp which can be used on beefy systems with lots of memory to
speed things up.
When running the integration tests downstream, it's useful to be
able to test that a new systemd version doesn't introduce any AVC
denials, so let's add a knob to make that possible.
Luca Boccassi
Daan De Meyer
Yu Watanabe